It is a well known fact hat deep drilling usually employs drill rods which are stiffly assembled from drill pipes and threaded pipe nipples. Upon rotation of the drill rod in one direction, threaded pipe nipples are able to transfer the torque.
The main disadvantage of rotary deep drilling performed with a drill rod as thus rigidly assembled is the slow operation, as is especially the case when frequent replacement of the drilling head is required. Then the drill rod must be disassembled into pieces and must be reassembled after the replacement of the drilling head
The drilling apparatus as disclosed in the U.S. Pat. No. 3,724,567 was developed for enhancing the quick drilling operation and avoiding frequent disassembly and assembly so that the drill rod can be raised from the drill hole without disassembling the drill rod. The drill rod can be laid into the series of carriages on a circular path with a diameter of about 100 m next to the boring tower, the carriages and path forming so-called drill rod receiver. The size of the drill rod receiver (i.e. storing unit) cannot be reduced, because the rigid drill rod is unable to tolerate increased bending without getting damaged. Moreover, due to the large dimensions and heavy weight of the apparatus, expensive drilling islands had to be developed for submarine drilling using it.
The Hungarian Patent Application (filed 4.09.1984) Ser. No. 3318/84 is also prior art and, discloses a continuously operated deep drilling apparatus for rotary deep drilling having two feed chains facing one another. The feed chains press the drill rod and rotate it via a rotary table. The feed chains also axially displace the drill rod up and down. This equipment enables assembly of the drill rod continuously from the drill pipes simultaneously with the drilling motion of the drill rod. This arrangement eliminates need for a tower and facilitates accelerated deep drilling while avoiding danger of tilting of the rod. However as in other known systems, he drill rod must be disassembled, e.g. into sections each consisting of a plurality of drill pipes if the drilling head is to be replaced. Thus in this case as well, there is the disadvantage that screwing and unscrewing of the drilling pipes require a considerable expenditure on labor connected with a significant loss of time.
The art has tried to eliminate deficiencies of the aforedescribed apparatus by deep drilling with hoses whereby drill rod is replaced by an endless flexible hose releaseable from a drum. In this case, means had to be provided for revolving the drilling head separately.
The principle of drilling the hole with a drilling motor or with a turbine is also known; however, these methods are unsuitable for deep drilling to depths of several thousands of meters.